Insulating bushing for electrical apparatus



March 18, 1930, A, ALLAN 1,751,379

, INSULATING BUSHIG FOR-ELECTRICAL APPARATUS vFvled March 4, 1926 3Sheets-Sheet 1 A. ALLAN Mach 1s, 1930.v

INSULATING BUSHING FOR ELECTRICAL APPARATUS Filed March 4 ,A 1926 3Sheets-Sheet 2 March 18, 1930.

A. ALLAN INSULATING BUSHING FOR ELECTRICAL APPARATUS Filed March 4',1926 3 Sheets-Sheet 3 it, lh@

.applicaties :nee time e, ieee, serial ne. e

This invention relates-to insulating bushings for high voltageelectrical apparatus and has for its object to prevent damage resulting'from the unequal expansion oi the different materials which. areemployed in the bushing and the parts it contains.

The insulating bushing according to the present invention comprises tivoexternal insulators in substantial alignment connected i@ together by amember serving as a support or the bushing and a central conductor whichis rigidly attached at one end to one ot the insulators Whilst its otherenel is free to slicle relative to the other insulator (for example i5by means oi a plug and socket or other sliciiug cormection) thearrangement being such as to permit relative longitudinal movementbetween the conductor ancl the insulators clue to the unequal expansionthereof.

rThe central conductor is preferably surrountled vvithin the externalinsulators by a condenser-insulator which is carried at an intermediatepoint by the supporting member Whilst its endsare lett tree to permitlongitudinal movement relative to the conductor ancl the externalinsulators and to allow, to some extent, for incorrect alignment. Thetubular metal core ot this condenser-insulator ,may be connected to thecentral coneluctor by means oi a llexible lead in orfler to maintainthem at the same potential and thus relieve intermecliary stress Withoutimpeding relative movement between them. rilhe supporting member mayconveniently take the form oi a casing containing a protective or othertransformer or the straight-through type.

Such a bushing maybe used with apparatus which contains oil, and. theopen spaces in the bushing itseli" may-be lled with oil. rllhus, i'orinstance, the central conductor may be one oir' those leading tothecontacts of an oilimmersed svvitch or circuit-breaker. in such a casethe central conductor is preferably ma le tubular or hollow and thesocketor sliding connection at its upper end is slottecl orotbervviseprovided; Wi

th an opening, so that oil may pass from the chamber surrounding thesoclret into the tubular conductor or vice versa anu the level of oil inthat chamber 5G may be kept approximately construit7 nnncrlarcananiversarios 53,269, anni in Great Ertan Haren lo,

bushing may be mounted on the oil tankx of the-switch or otheroil-immersed apparatus, so that the lovver insulator-and the open end oithe tubular central conductor are immersed in the oil, ancl thus the oilin the bushing and tubular conductor is in communication with that inthe tank. A reduction in pressure in the chamber surrounding the socketat the upper enrl the bushing will then draw oil up trom the tanl;through the tubular conductor, ancl conversely an increase oi2 pressurein that chamber would cause oil to ilovf clovvn the conductor into thetank. rllo prevent undue pressure in the bushing clue to heavy pressuresin the tank when the circuit is broken the lovver encl ci the tubularconductor may be provided with a ball or other valve, which is soarranged that it does not prevent a gradual flow oi oil in eitherdirection (lue say to temperature changes but prevents any rapid flowfrom the tenir into the bushing.

'l he invention may be carried into practice in various "Ways but threealternative constructions according thereto are illustrated 'by vvay or"example in the accompanying drawings, in which Figure i is an kelevationpartly in central section ot one construction,

Figure 2 is an enlargecl view (partly in section) of the upper end ofthe bushing shown in Figure l,

Figures 3 and et are views similar to those of Figures l ancl 2 butshowing the second construction,

lligure 5 is an enlargeol view o the lower end of the bushing shown inFigure 3, and

Figure 6 is a central section (partly in elcvation) of a simplerconstruction intended- {uore particularly'ior use in smaller bushin s.

ln the construction shown in Figures l and 2 the bushing consists ofupper an lower insulators-A A1 of porcelain or lilrematerial, which arecarried in alignment with one another respectively on cover B1 ancl onthe. base B2 of a transformer casing B having au external flange B3which acts as a support for the bushing. Either insulator may be formedin. tvvo or more parte clamped or cemented tot gna gether (as shown atA2 for the upper insulator A). The main conductorconsists of a rod Crigidly attached 'at its lower end C1 to the end of the lower insulatorA1 and passing centrally up through the upper end of the upper insulatorA. Surrounding the central conductor C is a metal core D1 on which iswound a condenser-insulator D of paper or other suitable material. Aange D2 ormed. in segments which are clamped around thecondenser-insulator D serves as a support therefor, the ends of thecondenser-insulatol` being left free to allow for longitudinal orlateral movementrelative tothe central rod C andthe external insulatorsA A1. rlhe transformer is located in its casing B around thecondenser-insulator D and the secondary windings thereof are connectedto termina-ls mounted in a box E carried on the outside o thetransformer casing B. The upper end of the central conductor C is formedas a plug engaging in a socket G which' is carried in the end of theupper insulator A and to which the incoming lead is connected. Thissocket is provided with a safety valve G1 to relieve excessive pressuresset up by abnormal conditions.

With this construction it will be seen that no undesirable strains areset up as a result of the different expansion of the various materialsused due to changes of temperature,

since the ends of the condenser-insulator D are free whilst the centralconductor C can slide in the socket G at its up er end.

The space between the condenser-insulator D and the external insulatorsA A1 is filled with oil, and in order to relieve the dielectric stresswhich might be set up between the conductor'C and the tubular Vcore D1of the vcondenser-insulator is the same in the construction of Figures 35 as in that'of Figures 1 and 2, and the same reference letters areemployedwhere applicable. rlhe central conductor is however dierentlyarranged in Figures 3 5 and will now be described.

In this construction the central conductor H is made tubular andprojects through the lower end of the lower insulator A1 to which it isconnected. rllhis lower insulator A1, and therefore also the end of theconductor H, is intended to be immersed in the oil contained in the tankof a transformer or of an oil-break switch a Contact H1 of which iscarried on the menare lower end of the conductor H. At its'upper end theconductor H slides in a socketKprovided with slots K1, so 'that theinterior of the tubular conductor H is in open communication with thespace within the bushing around the socket K.. Thus oil is free to flowfrom the tank through the tubular conductor H into the bushing or viceversa, and the level of oil in the bushing will be maintained more orless constant. ln order to prevent a rapid rush of oil from' the tankinto the bushing, such as might oc'cur when the switch 1s opened, a ballvalve H2 is provided in the lower end of the conductor H; This valve isso arranged that it will not prevent gradual How of oil in eitherdirection. The conductor H is as in the other construction connected tothe core D1 of the condenseninsulator D by means of a iiexible conductorH3.

Fi ure 6 illustrates a construction which may e employed in certaininstances, moreA especially in the case of a smaller bushing. In thisconstruction the bushing comprises upper and lower insulators L L1mounted respectively on the upper and lower ends of a transformer casinglvl having a flange M1 which serves as a support for the bushing.

The central conductor N is again xed to the lower insulator L1, but itsupper end is clamped within a member N1, the conductor N or an extensionN2 on the member N11 being arranged to slide within a machined hole inthe insulator L or within a metal bushing in a hole in the insulator.Connection with the external circuits may bemade by any suitable meansas for instance thoseindicate-d at N3 and N4. The central conductor N issurrounded by paper insulation C, which maybe of the condenser type ornot as desired. This insulation O may have its lower end fixed to theinsulator L1 and its upper end' free, to allow of longitudinal movementrelative to the central conductor and the external insulators.

It will be ap reciated that the three con2 structions have een'described by way of example only and that modiications may be madewithout departing from the invention.

What I claim as my invention 'and desire to secure by Letters Patent isl. An insulating bushing for high voltage electrical apparatus,comprising two external insulators in substantial alignment, a

connecting member between the insulators serving as a support for thebushing, a rigid central conductor fixed near one end to one of theinsulators, a conducting member lixed to the other insulator, and anelectrical connection between the free end of the central conductor andthe conducting member which is such Aas to allow longitudinal expansionand contraction of' the central conductor relative tothe externalinsulators. y

2. An insulating bushing for high voltage electrical apparatus,comprising two exter-` Manara connecting member between the insulators'serving as a support for the bushing, a central conductor which isrigidly attached near one end to one ot' the insulators whilst its otherend is tree to slide relatively to the other insulator, and an insulatorsurrounding the central conductor and so mounted within the bushing asto be tree to expand or contract longitudinally relativeV to theexternal insulators and to the central conduc tor.

3. 'An insulating bushing for high voltage electrical apparatus,comprising two external insulators'in substantial alignment, aconnecting member between the insulators serving as a support for thebushing, a central conductor which. is rigidly attached near one end toone of the insulators whilst its other end is tree to slide relativelyto the other insulator, a condenser-insulator surrounding thecentral'conductor within the bushing, and means whereby thecondenserinsulator is carried at an intermediate point by the supportingmember whilst its ends are left free to permit longitudinal 'movementrelative to the external insulators and to the central conductor.

l. Aninsulating bushing for high voltage electrical apparatus,comprising two external insulators in substantial alignment, aconnecting member between the insulators serving as a support for thebushing, a central conductor which is rigidly attached near one end toone of the insulators whilst its other end is tree to slide relativelyto the other insulator, a condenser-insulator having a tubular metalcore surrounding the central conductor within the bushing, va exibleconducting lead connecting the central conductor with the core of thecondenser-insulator, and means whereby the condenser-insulator iscarried at an intermediate point by the supporting member whilst itsends are left tree to permit longitudinal movement relative to theexternal insulators and to the central conductor.

5. An insulating bushing for high voltage electrical apparatus,comprising two external insulators in substantial alignment, a casingserving as a connecting member between the insulators and as a supportJfor the bushing and adapted to contain a transformer, a centralconductor which is rigidly attached near one end to one ot theinsulators whilst its other end is free to slide relatively to the otherinsulator, and an insulator surrounding the central conductor and somounted within the bushing as to be free to expand or contractlongitudinally relative to the external insulators and to the centralconductor.

6. An insulating bushing for high voltage electrical apparatus,comprising two external insulators in substantial alignment, a casingserving as a connecting member between the insulators and as a supportfor the bushing'and adapted to contain a transformer, a centralconductor which is rigidly attached .near one end to one of theinsulators whilst its other end is free to slide relatively to the otherinsulator, a condenser-insulator surrounding the central conductorwithin the bushing, and means whereby the condenserinsulator is carriedat an intermediate point by the transformer casing whilst its ends arelett ree to permit longitudinal movement relative tothe externalinsulators and to the central conductor.

7. An insulating bushing for high voltage electrical apparatus,comprising a member serving as a support for the bushing, two externalinsulators mounted in substantial alignment with one anotherrespectively on the upper and lower ends of the supporting member, acentral conductor, means for attaching the central conductor rigidly tothe end ot the lower insulator, a conducting meinber iixed adjacent theend of the upper insulator, a sliding connection of the plug-andsockettypev between such conducting member and the central conductor, andmeans ifor preventing the setting up of excessive internal pressureswithin the bushing. Y

8. An insulating bushing for high voltage electrical apparatus,comprising a casing having an external flange serving as a support forthe bushing, such casing being adapted to contain a transformer, twoexternal insulators mounted in substantial alignment with one anotherrespectively on the upper and lower ends 'of the transformer easing, acentral conductor, means for attaching the central conductor rigidly tothe end ot the lower insulator, a conducting member fixed adjacent theend of the upper insulator, a sliding connection of the plug-and-sockettype between such conducting member and the central conductor, and meansfor preventing the setting up of excessive internal pressures within thebushing.

9. An insulating bushing for high voltage electrical apparatus,comprising a' member serving as a support for the bushing, two externalinsulators mounted in substantial alignment with one anotherrespectively on the upper and lower ends of the supporting member, acentral conductor, means for attaching the central conductor rigidly tothe end of the lower insulator, a conducting member fixed adjacent theend of the upper i'nsulator, a sliding connection of the plug-and sockettype between such conducting member and the central conductor, means forpreventing the setting up of excessive internal pressures within thebushing, and a condenser-insulator surrounding the central conductorwithin the bushing and carried by the supporting member.

l0. An insulating bushing t'or high voltage electrical apparatus,comprising a member 'lil Aao

serving as a support for the bushing, two external insulators mounted insubstantial alignment with one another respectively on the upper andlower ends of the supporting member, a tubular central conductor rigidlyattached to the end of the lower insulator, a conducting member nedadjacent the end of the upper insulator, and a sliding connection ot theplug-and-socket type between such conducting member and the centralconductor, this sliding connection being slotted to allow oil to passfreely between the interior of the tubular conductor and the spacewithin the bushing surrounding such conductor.

ll. An insulating bushing for high voltage electrical apparatus,comprising a casing having an external ange serving asa support for thebushing, such casing being adapted to contain a transformer, twoenter-nal insulators mounted in substantial alignment with 'one anotherrespectively on the upper and lower ends of the transformer casing, asocket member xed adjacent the end ot the upper insulator, and a tubularcentral conductor rigidly attachedvto the end of the lower insulator andhaving its upper end formed as a hollow plug making sliding engagementwith the' socket member, such socket member being slotted to allow oilto pass freely between the interior of the tubular conductor and thespace within the bushing surrounding such conductor.

l2. An insulating bushing for high voltage electrical apparatus,comprising a member serving as a support for the bushing, two externalinsulators mounted in substantial alignment with one anotherrespectively on the upper and lower ends of the supporting member, atubular central conductor rigidly attached to the end of the lowerinsulator, a conducting member lined adjacent the end or the upperinsulator, a sliding connection of the plug-and-socket type between suchconducting member and the central conductor, this sliding connectionbeing slotted to allow oil to pass freely between the interior of thetubular conductor and the space within the bushing surrounding `suchconductor, and al valve in therlower end of the tubular conductor whichacts to prevent a rapid flow of oil up the conductor but allows agradual flow of oil'in either direction past the valve.

ln testimony whereof l have signed my name to this specication.

ARCHIBALD ALLAN.

